Cold air intake VS. Individual stacks? (ITB)
 

Need to replace one of the intake boxes on my Harrop so I'm researching which is better, the cold air intake pictured below or individual stacks. I guessed cold air intake. Looks like I may be wrong and individual stacks are better due to some pressure build up in the 'central air' set up.
Any one have the definitive answer? I've searched so much and read so much tech on ITB's and intakes my head hurts. Better = more HP and maybe drivability?- maybe.
thanks!

http://i232.photobucket.com/albums/e...GINESHOTHR.jpg

If you are talking about just putting filters on the end of the stacks and pulling in engine heated air, then I would say that you should stick with the current cold air package. Outside fresh cool air is always better then engine temp heated air for power and running more timing.

If you do change to individual filters and pull in engine temp air, most likely a retune in relation to AF and timing will be needed.

Did one side warp or crack?? Or did you have an "Oops" ??

Hope this helps.

Mike Norris

Dave Im thinking youd get more air from 8 52mm stacks as opposed to one 3" tube.
Im sure someone could do the math on this .
Ive seen many cars making big HP with open filters on the stacks

Mike, It had a surface crack for some time that grew into a crack? Kinda lame, those plastic boxes seem almost brittle. My thoughts were the same on the outside air. I'll try and dig up the tech regarding the subject, I think it was LS1.com. Long thread on ITB and the air intakes.

Jason your right somebody must have the simple math for us. It's two 3" tubes ...:rolleyes:

I've also asked Harrop, they must have the data.

here is one... stolen from LS1.com:

Originally Posted by 3.4camaro

8-50mm diameter tb's= 15705 sq. mm. surface area of throttle body.

1-105mm tb = 8654 sq.mm. surface area.

So the ITBs have a little less than twice the throttle blade surface area. Maybe that's why ITBs outflow a beck intake and tb.

In a ITB setup, each cylinder gets its own air supply. This means that each cylinder creates its own vacuum, and 1 cylinder doesn't suck on the supply of another cylinder. Maybe this raises the deltaP, because the air on the outside of the valve(in the intake runner) isn't being sucked(causing a low pressure) by another cylinder. This keeps the deltaP higher than it would be with a traditional single tb setup, and we all know a higher deltaP moves more air into the cylinder.

This make any sense to anyone?

----------

another snip from some where...

'The air boxes are for ****. If you buy a Harrop, the air box portion should be left in Aussie. Adding those boxes puts the performance of the intake back in line with a FAST 90. Even the guy at Harrop talked about how much they killed the power. I ordered mine with no air box and no plate that holds the air box. After I check fitment in the F-body chasis, I'll work on filtering the air.'

If that is true about the air boxes then why run them? I was thinking that if you modified your current 3" air tubes to feed the engine bay cool outside air while moving and went to the individual filters at the intake you MIGHT be able to get away with no tuning or maybe "less" tuning in consideration of the hotter under hood air you would have if you delete the air tubes all together.
I was thinking you could remove the filters from the current intake tubes, cut the tubes down in length so they do not protrude so far into the engine bay and maybe re direct the output end so it pushed the outside air up in the direction of the top of the motor. Does that make sense?
Of course it would do nothing while sitting in traffic, but while underway it should move a lot of cool air and help temps and breathing.
Just a thought.:cheers:

I guess the questions are (1) do you want to make more power and (2) does the engine have enough potential to support the full airflow of 8 ITB's?? One easy way to see if there is more in the engine is too see what the MAP sensor is doing at WOT. If the readings stay in the high 90's kpa, then it is doing pretty well. If the MAP is dropping to low 90's or even high 80's kpa, there is a signifigant restriction and more air should help.

I agree that the dual 3" tube are about a 35% drop of potential airflow, but going to dual 4" openings will equal it out and still allow fresh cool air.

I guess if it were me, and not knowing the potential HP of the engine beyond where it sets now, I would prefer to have the dual 3" openings and fresh cool air versus 8 ITB's and hot engine bay air. Now going to 3.5" dual tubes brings up the potential airflow by 25%.

Best scenario with re-engineering and retuning is dual 4" tubes to a slightly larger but similar plenum for each side.

A few options for sure. Hope this helps Dave.

Mike Norris

So I heard from Harrop, the boxes are not even sold with the intake anymore. Better performance without and most people did some thing unique. Below is a dyno graph comparing Harrop with- box / stacks / vs / FAST

http://i232.photobucket.com/albums/e...ne-vs-Fast.jpg


Mike helps a lot, thanks. I'll get back to you with details. More HP of course!
70rs not a bad thought but not really workable with current set up.

So looks like I'm shopping for some sort of stacks?

I understand. Like I said, just a thought. I would like to see what you come up with for a solution. Can you fit the carbon fiber stacks on that intake?
I forget the name of the project I saw them on here. Individual filters, really nice looking. Have no idea how well it functions though or if that is what you had in mind.

Kinsler IR intake I think you mean, ya that thing is sexy!! Something like that, they won't fit. (I'll double check)

I'll also need to address how air comes in and exits the engine compartment, like you mentioned.

Bingo! The Kinsler unit. Very nice!!

Where do the air intakes drop down to right now? If you remove those can you replace them with a fabricated "scoop" to get air from the same areas and just flood the engine compartment with good cool air?

http://www.usautoparts.net/bmw/image...ne/mclaren.jpg

itbs with properly designed airbox and a big enough feed pipe will be superior to open filters in the engine bay

look closely at the McLaren F1 engine above

those surface area calcs are bunk, remember that one cylinder will breathe at a time, so the surface area of the single throttle plate is fine, ITBs work by allowing pulse tuning/ tuned lengths. however with a 90 degree v8 the pulse tuning doesn't work as well as something like a ferrari v8 with a flat crank

I don't really know which direction to go, back and forth. The old set up worked so I'm thinking (with my wallet) maybe fix the box?

I don't know?

Bingo ! Just fix what you got, is the crack on the top, if yes maybe switch the box to teh other side and then it is on the bottom, you wont even be able to see it.

Good idea, thanks. Harrop did locate me a set if I need it (them- need to buy the set). Still doing research on the cold intake vs. the stacks (trumpets) Seems to be lots of varied theories.

Legend thanks Maclaren I'm sure did the research, sick looking engine!

Dave,
Did you make any decisions on the intake yet?

I did here you go: (sorry three year late reply...my kids- 3 and 5 and work took over priorities for a while, I'm back working/playing with FuEL)

I cut the existing boxes up and rebuild them bigger and way stronger the 3" has gone to 4" on both sides and 2" fatter through out every where else. Now to just make some 4" tubes running to air filters in similar location as the old air filter intakes...

Slowly tweaking other things as well.

I noticed this on a Ferrari and how they reduce air intake turbulence, the red extensions do nothing except mellow out the air flow. Sorry for the Ferrari pic but I thought it was interesting.